The invention relates to the 3D image reconstruction of dynamic objects from 2D projection images. The theory of image reconstruction demands a set of projection images of a stationary object over projection angles in the range of 200° (180°+cone angle). With a dynamic object an attempt is made to emulate a stationary object from said object. The imaging of the heart uses only the projection data that belongs to the heart phase during which the heart is practically at rest. This occurs in the end systole and in the end diastole.
Usually the heart phases are known from the EKG. The heart phase is specified relative to the heartbeat length between two QRS complexes (R wave) between 0 and 100%. The end systole is then located at around 30%, the end diastole at 70-90% for a heart rate of 60 bpm.
This is described for example in US 2008/0025590 A1 with reference to a method for temporal and three-dimensional presentation of a periodically changing structure, for example a heart, in which a number of rotation images are created. The rotation passes required are started offset by a specific angle for an identical event of the periodic process, initiated by the specified event in the EKG signal. New image series are assembled from the rotation images, with 3D image presentations able to be reconstructed for different phase areas of the period.
As an alternative there is the kymogram method in CT imaging, as is described by Kachelrieβ Et al. in “Kymogram detection and kymogram-correlated Image reconstruction from subsecond spiral computed tomography scans of the heart”, published in Med. Phys. 29(7), pages 1489 to 1503, July 2002. The kymogram method determines the focal point in the projection images and searches for phases with a focal point that remains the same. For the kymogram method the projection images must be complete in the transaxial direction. This however is not the case with C-arm computer tomography.